Supersonic fluidic switch

ABSTRACT

Fluid relays which operate with supersonic flow and remain stable irrespective of load impedance are disclosed. Isolation of the operating region of the relays from the receivers is accomplished by bleeding off the boundary layer about the outlet passages to cause total discontinuity in the subsonic portion of the fluid stream. The disclosed relays are also characterized by absence of an abrupt change in section where the fluid enters the operating region.

United States Patent Raymond V. Thompson Simsbury, Conn. 786,684 Dec. 24, 1968 Mar. 16, 1971 Chandler Evans Inc. West Hartford, Conn. Dec. 28, 1967 Great Britain lnventor Appl. No. Filed Patented Assignee Priority SUPERSONIC FLUIDIC SWITCH 7 Claims, 5 Drawing Figs.

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Field ofSearch "I:

References Cited UNITED STATES PATENTS 3,122,165 2/1964 Horton 137/81.5 FlSc l/04 137/81.5

3,135,291 6/1964 Kepler et al. 137/81.5 3,204,405 9/1965 Warren et a1. 137/81.5X 3,212,515 10/1965 Zisfein etal. l37/8l.5 3,262,466 7/1966 Adams et al. 137/81.5X 3,283,767 11/1966 Wright l37/18.5 3,326,227 6/1967 Mitchell l37/8l.5 3,380,655 4/1968 'Swartz l37/8l.5X 3,452,772 7/1969 Zaloudek 137/8 1 .5

Primary Examiner-Samuel Scott Attorney-Fishman and Van Kirk ABSTRACT: Fluid relays which operate with supersonic flow and remain stable irrespective of load impedance are disclosed. Isolation of the operating region of the relays from the receivers is accomplished by bleeding off the boundary layer about the outlet passages to cause total discontinuity in the subsonic portion of the fluid stream. The disclosed relays are also characterized by absence of an abrupt change in section where the fluid enters the operating region.

SUQIERSONIC FLUIDIC SWITCH BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fluidics. More particularly, the present invention relates to fluid devices such as switches and relays which operate with supersonic flow. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.

2. Description of the Prior Art The rapid development of devices such as ballistic missiles in which the mechanism for controlling the functions or movements of the device must be of light weight has caused considerable attention to be given to the subject of fluidics. Fluidics may be defined as the field relating to the control of apparatus by jets of high velocity fluid.

One of the most important devices in the field of fluidics is the fluid relay. in their present form, fluid relays consist of a casing defining a reaction chamber or operating region which i is narrower at one end than at the other. The casing is formed with an inlet nozzle which discharges into the narrow end of the reaction chamber and an outlet passage or passages leading from the other end of the reaction chamber. In previous fluid relays, the narrow end of the reaction chamber is wider than the discharge end of the inlet nozzle. One and generally two control ports, the ports facing one another and having axes which are oriented transversely to the axis of the inlet nozzle, are located at the narrow end of the reaction chamber. The inlet nozzle and the control ports are connectable to sup plies of gas under pressure, the usual operating pressure being somewhere between 5 and p.s.i. In the operation of such prior art fluid relays, a stream of fluid issuing from the inlet nozzle moves into the divergent reaction chamber and, owing to irregularities in the flow and asymmetry in the shape of the chamber, the fluid stream bends to one side or the other before flowing into an outlet passage nearer that side. By admitting fluid under pressure to the control port on the side of the chamber toward which the main or power stream of fluid discharging from the input nozzle is bent, the power stream can be caused to swing to the opposite wall of the reaction chamber so that it is then directed into the other outlet passage. A comparatively small quantity of low pressure control fluid can thus control a jet powerful enough to perform control or propulsion functions when directed into the appropriate outlet passage.

The above briefly described low pressure relays of the prior art operate by the aid of the Coanda effect. This effect may be briefly stated as the tendency of a fluid in motion to flow along a surface and follow the contour of the surface even when the surface is curved away from the direction of flow of the fluid. ln employing the Coanda effect, it has been necessary to utilize fluid at comparatively low pressure so that the velocity of the power stream issuing from the input nozzle is low and subsonic. Thus, the pressure in the power stream issuing from the input nozzle of prior art fluid relays is superatmospheric and,

because the pressure is superatmospheric and also because of the tendency of the stream of fluid to adhere to one wall or the other of the reaction chamber, the control fluid applied through the control portmust also be superatmospheric in pressure. Because of the tendency of the stream issuing from the nozzle to adhere to one wall or the other of the reaction chamber, it has been necessary to form prior art fluid relays in such a manner that the stream issuing from the input nozzle cannot contact a wall of the immediately as it leaves the nozzle. This design requirement is necessary in order to provide a space within which the control fluid may operate transversely against the stream issuing from the input nonle. In order to provide the reaction space, prior art fluid relays are formed in such a manner that the narrow end of the chamber is wider than the discharge .end of the power stream nozzle entering the chamber. This is usually referred to as offsetting the control ports and the amount by which the control ports are offset is usually referred to as set back." In summary, known fluid relays operate mainly on simple mechanical principles whereby the pressure of the control fluid simply pushes the power stream of fluid issuing from the nozzle in a transverse direction and forceably detaches it from the wall of the chamber along which it was flowing and causes it to move by a form of snap action over to the other side of the chamber where it attaches itself to the other wall.

As missiles become larger, the power required to control and/or propel them becomes greater and the power available from the known types of fluid relays has become inadequate without making such relays uneconomically large and also requiring excessively large volumes of operating and control fluid. Attempts have been made to enhance the output power of fluid relays by increasing the pressure of the fluid and par ticularly by increasing the pressure to such an extent that the fluid injected into the reaction chamber leaves the nozzle with supersonic velocity. While it has been found possible to operate fluid relays of the prior art types briefly discussed above with fluid at a pressure sufficiently high to provide supersonic velocities, use of supersonic flow has usually resulted in instability and successful operation has been found to be highly dependent upon the impedance against which the fluid stream is operating. This dependence upon load makes it quite impractical to use high-velocity fluid relays for many applications since it requires that each relay be matched to the impedance against which it must operate. Much research work has been conducted in an endeavor to provide a relay design which will provide high output power while being of comparatively small size. Such research efforts have so far been unsuccessful since, in all cases, it has been impossible to eliminate the difficulty mentioned above wherein operation of the relay is influenced by the impedance against which it operates and any changes in such impedance can make a relay which had previously been operating more or less successfully become erratic in its operation. For missile control any possibility of erratic operation of a device makes its use out of the question.

SUMMARY OF THE INVENTION It is an object of the present invention to provide high-pressure fluid relays which provide high output power in small size and which remain stable in operation irrespective of the impedance against which it is to operate.

A fluid pressure relay in accordance with the present invention incorporates a casing enclosing a chamber which is narrower at one end than at the other. The casing is formed with an inlet nozzle which discharges into the narrow end of the chamber, there being no set back" or abrupt change in the area presented to the high velocity stream as it discharges from the nozzle. The inlet nozzle is proportioned to promote the discharge of a jet moving at supersonic velocity when supplied with fluid atsufi'icient pressure. The casing has at least one outlet passage leading from the opposite or wide end of the chamber and two control ports which communicate with the chamber from opposite sides thereof at points intermediate the narrow and wide ends thereof, the axes of the control ports being in the same plane as the axis of the outlet passage or passages.

For thrust-vector control, that is for use in rocket-type vehicles, the relay is provided with a single outlet passage having a width which is large in comparison with the width of the chamber. Change of direction of thrust, with a single outlet passage, is achieved by moving the issuing jet from one side of the outlet passage to the other.

For use with a pressure-operated device, in order to control and/or provide the operating force necessary, the chamber is formed with two outlet passages so located that the axes of the control ports and of the outlet passages are substantially in the same plane. in addition, boundary layer bleedoff ports, for example in the form of supersonic diffusers, are provided. The boundary layer bleedoff ports completely surround the en'- trances of the outlet passages so that the receivers are not physically connected with the operating region. Obviously, if deemed necessary or desirable, an additional pressure-relief passage incorporating a restriction or a pressure-relief valve may be connected in each outlet passage.

BRIEF DESCRIPTION OF THE DRAWING The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawing wherein like reference numerals refer to like elements in the various FIGS. and in which:

FIG. I is a cross-sectional, top view of a first embodiment of the present invention, the embodiment of FIG. 1 having a single outlet port.

FIG. 2 is a cross-sectional, top view of a second embodiment of the present invention, the embodiment of FIG. 2 having a pair of outlet ports.

FIG. 3 is an enlarged, partial, cross-sectional, top view of the embodiment of FIG. 2 with the addition of diffuser means for achieving boundary layer bleedoff and permitting pressure recovery, the diffuser means being shown schematically. FIG. 4 is a schematic, partial, side elevation view of a portion of the embodiment of FIG. 3.

FIG. 5 is an enlarged, cross-sectional view of a portion of the embodiment of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the operation of the present invention, fluid of a pressure sufficiently high to cause the stream issuing from the input nozzle into the chamber to reach supersonic velocity is fed to the nozzle 12 while the control ports 14 and 16 are left closed to the ambient pressure. Normally the fluid stream, because of dissymmetry in chamber 10, will bend toward one side of the chamber or the other. The stream can be directed to the side opposite to that which it is bent by merely opening to the ambient pressure the control port on the side of the chamber towards which the stream is presently attached. For very fast and positiveswitching, instead of opening or blocking the appropriate control port, control fluid at above ambient pressure may be introduced to the port. It has been found by experiment that the present fluid relay provides, for a given size, an output force much higher than is obtainable from a fluid relay operating at a pressure such that the main jet moves at subsonic velocity.

In the relay constructed for use with a pressure-operated device, for example as shown in FIGS. 3-5, the boundary layer bleetloff ports 18 and 20, defined by respective diffusers 22 and 24, isolate the receivers from chamber 10 and thus prevent changes in the impedance against which the relay is working from affecting operation of the relay. The foregoing results because the boundary layer bleedoff ports bleedofi the boundary layer of the stream of fluid, causing total discontinuity in the boundary layer, thereby preventing feedback from the outlet passages into the chamber (operating region) via the subsonic portion of the boundary layer whereby the conditions prevailing in the outlet passages cannot influence what takes place in the chamber. In this manner, complete stability of operation of the relay is achieved and the load is isolated from the operating region.

The high gain obtainable with the present invention may be simply stated as being the result of changing the pressure energy of the incoming fluid to velocity energy to such an extent that its pressure is subambient, providing means for acting on the main stream of fluid with control fluid at ambient pressure and then reconverting the velocity energy of the main stream fluid to pressure energy. Since the control fluid is already at ambient pressure, which is higher than the pressure prevailing at the point where the energy of the stream is mainly velocity energy, it is necessary only to open the appropriate control port to the ambient pressure and thus control operation may be achieved by merely venting to atmosphere.

To briefly review the distinguishing features between the present invention and the prior art, it has previously been found necessary to provide an abrupt change of section, that is a set back, at the point where the inlet nozzle discharges into the diverging reaction chamber. The set back has previously been necessary to prevent the jet issuing from the nozzle from attaching itself immediately to one wall of the chamber. The jet issuing from the inlet nozzle of prior an devices is thus projected into the chamber and maintains approximately its original sectional dimensions as it moves into the chamber and does not come against and attach itself to one wall or the other until it has moved a certain distance down the chamber. A pocket is formed between the issuing jet and the portion of the wall of the chamber at the inlet nozzle end of the chamber and the presence of this pocket is essential for reception of control fluid to cause the jet to be deflected. Consequently, the control ports must be located at the entry end of the chamber so that they can feed control fluid into the pockets.

It has been found that, when fluid at a pressure sufficiently high to cause flow at supersonic velocity is fed to the prior art devices having a set back," the stream issuing from the inlet nozzle, instead of being projected into the chamber and coming against the side of the chamber some distance down the chamber, immediately spreads out and fills the narrow end of the chamber. Under these conditions, the control fluid has an effect on the supersonic jet which depends largely on unpre dictable characteristics of the jet. Because of the instability produced by the introduction of the main jet and the control jets, the impedance against which the main jet is to operate becomes all important. Also the control fl'uid must be at superatmospheric pressure and, since the control is kinetic, the minimum pressure of the control fluid is always a function of the pressure of the main operating fluid.

In accordance with the present invention, the gradual change of section where the nozzle enters the chamber causes the supersonic jet to diverge and fill the small end of the chamber and move along in contact with both divergent walls of the chamber until a point is reached where the momentum forces in the boundary layers of the jet are balanced by forces produced in the stream by the ambient pressure at the outlet end of the chamber. The jet thereupon leaves the divergent walls of the chamber. The prevailing pressure conditions and velocity conditions in the separated boundary layers on each side of the stream cause the boundary layers of the stream to mix turbulently with the surrounding ambient atmosphere and tends to produce a zone of subambient pressure on each side of the main stream. Because of the asymmetry always present in any structure and the basic instability of the stream, the turbulent mixing action is of greater magnitude adjacent one wall of the chamber than adjacent the other. Thus, there is a transverse force unbalance acting on the-stream and the stream moves over and reattaches itself to one wall. When the stream reattaches to one wall, a space is enclosed in which recirculating flow, at a pressure below atmospheric but above the pressure in the main stream of fluid, takes place. The stream is now quite stable and flows through the outlet passage adjacent the wall to which it is attached. The control ports of the present invention are located in the portion of the chamber walls downstream from the latest separation point but upstream from the earliest reattachment point of the main stream within the pressure limits of operation of the device. Switching of the stream from one wall to the other, and thus from one outlet passage to another, is effected merely by opening to the ambient pressure the control port on the side to which the stream is inclined while closing the oppositely disposed port. This results in an increase in the pressure in the enclosed zone from subambient to ambient. The transverse unbalance across the stream then has the opposite sense and the stream swings over to the opposite wall. As the pressure in the enclosed zone is subambient and switching is effected merely by raising its pressure to ambient, no source of control pressure at superarnbient pressure is required and the switching action is independent of the pressure of the fluid supply and of the impedance against which the relay is operating. The present invention also provides the additional advantage of higher power for a given size as compared with a conventional relay because of the use of high pressure fluid.

The pressure relief passages, such as passages 26 of FIG. 3, may include valves and where provided prevent abuild up of pressure if the outlet passages should be closed off or restricted for any reason.

In most applications of the relays of the present invention, the ambient pressure will be atmospheric pressure,. but there may be occasions where the ambient pressure will be superatmospheric or subatmospheric. I

While preferred embodiments have. been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

lclaim:

1. A fluidic switch comprising:

an operating region defined by at least ;a pair of diverging sidewalls;

means for delivering fluid under pressure to said operating region, said delivery means discharging fluid into the narrow end of said operating region, said delivery means and operating region cooperating to induce supersonic flow in said operating region;

at least a first control port, said port communicating with said operating region through one of said diverging sidewalls and being positionedintermediate the ends of said sidewall; 1

at least a first outlet passage at the wide end of said operating region;

receiving means positioned adjacent said outlet passage to receive fluid exiting from said operating region; and

means defining a continuous boundary layer bleed port about the periphery of said outlet passage between said receiver means and the walls of said outlet passage. 2. A fluidic switch as in cm. 1 wherein: 'said receiver means and the walls of said outlet passage cooperate to define said bleed port. 7 3. The apparatus of claim 1 further comprising: i at least a second control port, said second port communicating with said operating region through a second diverging sidewall and being positioned intermediate the ends of said wall.

4. The apparatus of claim 3 wherein said control ports are located in the diverging sidewalls downstreamof the latest separation point and upstream of the earliest reattachment point of the supersonic stream of fluid within the pressure limits of operation of the apparatus.

5. The apparatus of claim v4 wherein said control ports selectively provide communication between said operating region and the ambient atmosphere. 7

6. A supersonic fluid control device comprising:

a chamber having a pair of outlet passages at a first end thereof and a pair of oppositely'disposed control ports in the sidewalls thereof; Y means for discharging a supersonically flowing'stream of fluid into said chamber from the second end thereof; and receiver means juxtapositioned'to said outlet passages and defining a continuous boundary layer bleed ports about the periphery of the outlet passages.

7. The apparatus of claim 6 wherein said receiver means comprises:

a supersonic difiuser positioned adjacent to each of said outlet passages. 

1. A fluidic switch comprising: an operating region defined by at least a pair of diverging sidewalls; means for delivering fluid under pressure to said operating region, said delivery means discharging fluid into the narrow end of said operating region, said delivery means and operating region cooperating to induce supersonic flow in said operating region; at least a first control port, said port communicating with said operating region through one of said diverging sidewalls and being positioned intermediate the ends of said sidewall; at least a first outlet passage at the wide end of said operating region; receiving means positioned adjacent said outlet passage to receive fluid exiting from said operating region; and means defining a continuous boundary layer bleed port about the periphery of said outlet passage between said receiver means and the walls of said outlet passage.
 2. A fluidic switch as in cm. 1 wherein: said receiver means and the walls of said outlet passage cooperate to define said bleed port.
 3. The apparatus of claim 1 further comprising: at least a second control port, said second port communicating with said operating region through a second diverging sidewall and being positioned intermediate the ends of said wall.
 4. The apparatus of claim 3 wherein said control ports are located in the diverging sidewalls downstream of the latest separation point and upstream of the earliest reattachment point of the supersonic stream of fluid within the pressure limits of operation of the apparatus.
 5. The apparatus of claim 4 wherein said control ports selectively provide communication between said operating region and the ambient atmosphere.
 6. A supersonic fluid control device comprising: a chamber having a pair of outlet passages at a first end thereof and a pair of oppositely disposed control ports in the sidewalls thereof; means for discharging a supersonically flowing stream of fluid into said chamber from the second end thereof; and receiver means juxtapositioned to said outlet passages and defining a continuous boundary layer bleed ports about the periphery of the outlet passages.
 7. The apparatus of claim 6 wherein said receiver means comprises: a supersonic diffuser positioned adjacent to each of said outlet passages. 